Changing the rotation of a Trigger makes the Trigger not work anymore?

I want to make it so if a player walks by a security camera, it follows the player. Thing is, changing the rotation of the camera makes the OnTriggerEnter even not fire anymore.

My code, so far, was

 void OnTriggerEnter (Collider Cone) {
     if (Cone.gameObject.CompareTag ("Player")) {
         Debug.Log ("Inside");
         _playerIsSeen= true; 
 }
 void OnTriggerExit (Collider Cone){
     if (Cone.gameObject.CompareTag ("Player")) {
         Debug.Log ("Out");
         _playerIsSeen= false; 
     }
 }
 void Update (){
         if (_playerIsSeen){
               _camera.transform.LookAt(_player.transform.position);
         } else {
               _camera.transform.LookAt(_idlePoint1.transform.position);
         }
   }

The problem is, as soon as the camera moves, then OnTriggerEnter refuses to fire ever again. Either that, or OnTriggerExit keeps firing forever. The end result is that the camera snaps to the player for a millisecond before resuming staring at its default position forever, even if the player tapdances in front of it.